Abstract. The primary sources and atmospheric chemistry of C2-C5 alkanes were
incorporated into the atmospheric chemistry general circulation model EMAC.
Model output is compared with new observations from the NOAA/ESRL GMD
Cooperative Air Sampling Network. Based on the global coverage of the data,
two different anthropogenic emission datasets for C4-C5 alkanes,
widely used in the modelling community, are evaluated. We show that the model
reproduces the main atmospheric features of the C2-C5 alkanes (e.g.,
seasonality). While the simulated values for ethane and propane are within a
20% range of the measurements, larger deviations are found for the other
tracers. According to the analysis, an oceanic source of butanes and pentanes
larger than the current estimates would be necessary to match the
observations at some coastal stations. Finally the effect of C2-C5
alkanes on the concentration of acetone and acetaldehyde are assessed. Their
chemical sources are largely controlled by the reaction with OH, while
the reactions with NO3 and Cl contribute only to a little
extent. The total amount of acetone produced by propane, i-butane and
i-pentane oxidation is 11.2 Tg/yr, 4.3 Tg/yr, and 5.8 Tg/yr,
respectively. Moreover, 18.1, 3.1, 3.4, 1.4 and 4.8 Tg/yr of acetaldehyde are formed by the oxidation of ethane, propane,
n-butane, n-pentane and i-pentane, respectively.